Slider
FREEAdjustable slider with bidirectional feedback
When to reach for it
Slider commands a single continuous value over a topic: motor PWM, servo angle, gripper width, a velocity setpoint. Turn on Track Robot State (Pro) for a feedback ghost as the robot converges on the command. Reach for Knob when the control should feel like a rotary dial, or Joint Sliders (Pro) for more than one joint at once.
Worked example: gripper width
A parallel gripper with an 85 mm stroke, driven by a node expecting a position setpoint. Topic /gripper_width_cmd, schema std_msgs/msg/Float64. Min 0.0, Max 0.085, Step 0.001. Turn on Publish on Release Only: a gripper needs one final width, not the whole drag. Leave it off, the factory default, for a live setpoint like a target velocity.
Watch out for
- Min Value, Max Value, and Step are the scale the app enforces, not a safety limit. The robot does whatever value you send, so match them to the receiver.
- The outbound message is always shaped
{ "data": <value> }, whatever Schema Name says. It fitsstd_msgs/msg/Float64orFloat32; a schema needing the value under a different key never gets it. - On Pro, if Track Robot State is on and feedback never settles within Recouple Timeout (ms), the thumb auto-jumps to feedback rather than stay stranded. A teleporting thumb means the controller stalled, not a broken widget.
Configuration fields
The topic this widget publishes to. While connected, tap to pick from the topics the robot advertises.
The ROS message type for this topic, e.g. sensor_msgs/msg/Image. Usually auto-filled when you choose a topic.
Send one value when you release the thumb, instead of streaming continuously while you drag.
How fast the slider streams updates when the user is dragging.
WITH PRODefault is 10 Hz. Tight servos and position controllers feel smoother at 20 to 50 Hz when sweeping the value quickly. Lower it to 5 Hz on bandwidth-constrained links to save throughput. No effect when "Publish on Release" is on.
Show the robot's actual value as a ghost indicator alongside your command.
WITH PROThe widget subscribes to a feedback topic and renders the live state as a ghost on the track. The thumb stays at your commanded value, so you see command and state diverge during motion. On first connect, the thumb snaps to the actual value so the first interaction starts from where the robot is.
Topic carrying the robot's actual value, drawn as a ghost alongside your command.
Field path on the feedback topic to read as the actual value.
After release, the thumb stays at your commanded value while feedback catches up. If feedback never settles within this window (slow controller, no controller listening), the thumb auto-recouples to feedback anyway.
500 to 10000, step 500Ease the ghost and thumb toward the robot's reported value instead of snapping to every sample.
WITH PROApplies a light exponential smoothing to the displayed feedback only. Softens a jumpy or noisy controller. Your commanded value and out-of-range detection are unaffected.
How strongly to ease the displayed feedback. Light barely softens; Heavy strongly damps a noisy controller at the cost of more lag.
Show a name on the widget.